(1) Investigation of the interaction and relationship of the respiratory chain with the ATP synthesizing complex during vigorous oxidative phosphorylation, particularly by continuous testing of the chemical coupling theory and the most recent conformational coupling hypothesis. The latter theory predicts that ligands of ATPase may cause a conformational change in the respiratory components resulting perhaps in distinct perturbations of redox components which can be detected by modern spectroscopic methods. (2) The study of mutants of Azotobacter vinelandii in which primary defects in the respiratory chain (e.g. deletion or modification of cytochrome) have been induced. A unique mutant of A. vinelandii has been isolated which is deficient in c-type cytochromes and which has revealed novel b-type species which are high wavelength and whose appearance is apparently energy-dependent. (3)The study of purified A. vinelandii NADH dehydrogenase, a functionally competent multi-iron-sulfur flavoprotein which undergoes an unusual spectral interaction with the uncoupler-inhibitor dicumarol, as a possible model system for investigating the mechanisms of action of uncoupling of energy conservation. (4)Preparation of intact energy coupling sites and the direct study of interaction between the respiratory components and ATPase without any possible interference from a proximal energy coupling site. (5) The study of cytochrome c3-the multi-heme, auto-oxidizable hemoprotein as a model system for cytochrome c oxidase and for energy-linked changes at the energy coupling site II. (6) The role of the iron-sulfur components in energy conservation by determining whether biological ligands can induce by conformational changes in protein structure the possible interconversion of high-potential and low-potential iron-sulfur clusters found in the respiratory chain. As a model system adenylyl sulfate (APS) reductase--a multi-iron-sulfur flavoprotein--will be studied. This enzyme is involved in the formation of APS, a very high-energy compound delta G' approximately or equal to - 18 kcal).